Monothiazyl dithiocarbonates and method for preparing same



Patented July 30, 1946 MONOTHIAZYL DITHIOCARBONATES METHOD FOR PREPARING SAME Edward S. Blake, Nitro, W. Va., assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Original application February 26,

1941, Serial No. 380,677. Divided and thisapplication June 23, 1943, Serial No. 491,921

18 Claims. (01. 260-306) The present invention relates to new vulcanization accelerators, to a process of vulcanizing rubber and to the vulcanized rubber products obtained with the aid of said new accelerators.

The accelerators of this inVention are the monothiazyl dithiocarbonates. This class of ma terials is represented by the structural formula 'as-c-s-ra t v where R2 may be one of a wide variety of suitable substituting groups in which carbon is linked to the sulfur as hereinafter disclosed and R1 is a thiazyl radical. Typical examples of the latter comprise benzothiazyl, methyl thiazyl, methyl benzothiazyl, nitro benzothiazyl, chlor benzethiazyl, amino benzothiazyl, 4 phenyl benzothiazyl, naphthothiazyl, dihydrothiazyl (thiazolyl) and 6 phenyl benzothiazyl radicals. While the aforementioned radicals are illustrative of some of the thiazyl radicals which may be em ployed, the invention is by no means limited thereto.

While the new compounds ma be employed alone as vulcanization accelerators they are used with greater advantage in conjunction with basic nitrogen containing accelerators as activators thereof and are preferably so employed. As suitable basic nitrogen containing accelerators there may be mentioned diphenyl guanidine, 'di-o-tolyl guanidine, thiocarbam'lide, hexamethylene tetra mine, para phenylene diamine, anhydro formaldehyde aniline, diphenyl guanidine phthalate, triphenyl guanidine and butylaldehyde aniline.

' Again the foregoing list is by no means complete being illustrative of activators which may be used with the new accelerators but it is in nowise limitative of the invention.

The new accelerators may be prepared by methods well known to chemists. For example they may be manufactured by reacting a mercaptothiazole, usually in the form of a metallic salt such as a Zn, K or Na salt, and a thio ester of chloro carbonic acid. Somewhat better yields are obtained by carrying out the reaction in an organic solvent such as alcohol although aqueous solution may be used where desired, in which case a water soluble salt of the thiazole should be used. A thio ester of chloro carbonic acid may in turn be prepared by reacting phosgene with a mercaptan or thio phenol. Thus, onehalf molecular proportion of ethyl mercaptan was dissolved in dry decalin and this solution added to a solution of one molecular proportion of phosgeue dissolved in dry decalin containing a and gradually allowed to come to room temperature. After HCl had ceased to be evolved the product was distilled from the solvent under a mild vacuum and purified by distillation. Low

boiling solvents have been used with equally good results in which case the solvent is removed first,

preferably by distillation, and the residue purified as described. The pure thio ethyl chlor carbonate boiled at 129-132 C'. This product was reacted with the sodium salt of mercaptobenzothh azole in aqueous solution and also with the potassium salt of mercaptobenzothiazole in ethyl alcohol. It will be appreciated that other solvents may be used in either step and other metallic salts or. even the free mercaptothiazoles may be used where desired.

Other mercaptans and thio phenols which may be used for preparing the new accelerators include methyl mercaptan, propyl mercaptan, butyl mercaptan, amyl mercaptan, thio phenol, benzyl mercaptan, lauryl mercaptan, nitrophenyl mercaptan, thio cresol, 'xylyl mercaptan, pinene mercaptan and cyclohexyl mercaptan. Thus, R2 in the above formula may be an alkyl, aralkyl, aryl or alicyclic radical including terpene radicals.

desirable results attainable thereby, but without limiting the invention, rubber stocks were compounded comprising Stock Stearic acid Bcnzothiazyl, benzyl d1- thiocarb onate l Benzothiazyl, propyl d1- thio carbonate Benzothiazyl, ethyl d1- thiocarbonate Benzothiazyl. butyl dithiocarbonata.

The stocks so compounded were vulcanized in a press by heating for different periods of time at the temperature of twenty pounds steam pressure-per square inch. The modulus and tensile properties of the cured rubber products are set forth below. i e

As specific embodiments of the invention illus-, trating the use of the new accelerators and the As noted, the new accelerators are used with particular advantage in conjunction with basic nitrogen containing accelerators asactivators thereof. As exemplary of such use but again without limiting the invention, rubber stocks were compounded comprising Stock E F G H .7

Parts by Paris by Parts by Parts by Parts by weight weight weight weight weight Pale crepe rubber 100 100 100 100 100 Zinc oxide 5 5 5 5 Sulfur. 3 3 3 3 5 Stearic ac o. s 10. 5 0. 5 0, 5 0,5 Diphenyl guanidlne 0. 15 0.15 0. l5 0. 15 0.15 Benzothiazyl, ben'zyl dithiocarbonatm 0. 6 Benzothiazyl, propyl di thiocarbon'ate 0.6 Benzothiazyl, plienyl dithiocarbonate 0.6 Benzothiazyl, ethyl di- ,thlocarbonate 0.6 Benzothiazyl, butyl dithiccarbonate; 0.6

- The stocks so compounded were Vulcanized in the same manner as stocks A-D the vulcanizing temperature being as before, the temperature of twenty pounds of steam pressure per square inch. The modulus and tensile propertiesof the cured rubber products are set forth below:

Table Ii Mozduluslgf lelas tic T n iyln sin. a ens e S-tbck gr g elo'ngations oi' at break 2 2 minutes lbs l mfi percent 45 450 1, 74b 3, 350 820 45 415 1, 700 3, 450 820 45 330 l, 230 2, 870 830 45 410 1, 860 3, 100 780 45 335 l, 160 3, 275 870 90 630 2, 450 3, 850 785 90 525 2, 255 3, 950 800 90 420 1, 670 3, 290 810 90 640 2, 650 3, 550 V 750 90 410 1, 460 3, 435 840 The data set forth in Tables I and II show the desirable physical properties of vulcanizates cured in the presence of the new accelerators alone and in conjunction with basic nitrogen containing accelerators as activators thereof. Moreover, although the mixture of accelerators is effective and fast, it is not so fast in action as to produce prevulcanization or scorching of the stock during the milling, calendering or other handling operations.

Again resort may be had to other methods of preparing the new accelerators Where convenient or desirable. This invention is not concerned with the preparation of the compounds and is not in any Way limited thereto. Furthermore, the

present invention is not limited to the specific examples hereinbefore set forth wherein the preferred accelerators are employed. Other ratios of the compounding ingredients than those men- 5 tioned in the examples as Well as other Well known fillers, pigments and the like may be employed in the production of various types of rubber compounds and are apparent to those skilled in the art to which this invention pertains. The invention is limited solely by the claims attached hereto as part of the present specification.

This application is a division of co-pending application Serial No. 380,677, filed February 26, V

1941, Patent 2,336,217,

What is claimed is:

.1. The chemical product comprising a mono thiazyl dithiocarbonate in which the said thiazyl radical is linked to one sulfur atom of the dithiocarbonate nucleus and a radical selected from the group consisting of alkyl, aralkyl, aryl, alicyclic and terpene radicals is directly' linked to the second sulfur atom of the same dithiocar bonate nucleus.

2. The chemical product comprising a compound possessing the structure R,-si-s-R where-R1 is a thiazyl radical and R2 is a radical 36 containing carbon and hydrogen only.

3. The chemical product comprisinga com= pound possessing the structure where R1 is an aryl thiazyl radical and R2 is a radical containing carbon and hydrogen only.

4. The chemical product comprising a compound possessing the structure ar sa s s? where R1 is a benzothiazyl radical and R2 is a radical containing carbon and hydrogen only.

415 5. The chemical product comprising a compound possessing the structure U R1''S-G'S' R2 '5 Where R1 is a benzothiazyl radical and R2 is an '7. The chemical product comprising "compound possessing the structure SJIhe: chemical product comprising 1 5 Pound possessing the structure 9. The-method of making a monothiaz'yl-diwhere R2 is a hydrocarbon radical.

11 The method of making a monothiazyl dithiocarbonate which comprises reacting a mercapto aryl thiazole with a product of the structure where R2 is a hydrocarbon radical.

12. The method of making a monothiazyl dithiocarbonate which comprises reacting mercaptobenzothiazole with a product of the structure where R2 is a hydrocarbon radical.

13. The method of making a monothiazyl dithiocarbonate which comprises reacting mercaptobenzothiazole wtih a product of the structure where R2 is an aliphatic hydrocarbon radical con taining less than 5 carbon atoms.

14. The method of making benzothiazyl ethyl dithiocarbonate which comprises reacting mercaptobenzothiazole with ethyl mono thio chlor carbonate the ethyl radical being linked to the sulfur atom.

15. The method of making benzothiazyl benzyl dithiocarbonate which comprises reacting mercaptobenzothiazole with benzyl mono thio chlor carbonate the benzyl radical being linked to the sulfur atom.

16. The method of making benzothiazyl phenyl dithiocarbonate which comprises reacting mercaptobenzothiazole with phenyl mono thio chlor carbonate the phenyl radical being linked to the sulfur atom.

17. The method of makinga monothiazyl dithiocarbonate which comprises reacting phosgene with an aliphatic mercaptan under substantially anhydrous conditions to remove one of the chlorine atoms as HCl and condensing the product with a. mercapto thiazole in the form of its alkali metal salt.

18. The method of making a monothiazyl dithiocarbonate which comprises reacting phosgene with a thio phenol under substantially anhydrous conditions to remove one of the chlorine atoms as HCl and condensing the product with a mercapto thiazole in the form. of its alkali metal salt.

EDWARD S. BLAKE. 

